Multiple-antenna techniques, often referred to as multiple-input-multiple-output (MIMO) techniques, enable communication with increased spectral efficiency, either through linear beamforming which enhances signal-to-noise ratio (SNR), spatial multiplexing which enhances data rate through multiple parallel streams, or spatial diversity which enhances link reliability.
MIMO systems that leverage multiplexing or diversity gains typically require space-time array signal processing that can practically only be implemented in the digital domain, and thus require digitization in each antenna signal path. A digital array also enables powerful digital array calibration. However, since the spatial processing is only performed in the digital domain, RF/analog spatial filtering is forsaken, leaving the RF/analog circuits and the data converters exposed to all the spatial content that is present at the antenna aperture, desired or not. In the presence of strong interference signals, such an architecture requires high instantaneous dynamic range from the RF/analog circuits and the data converters, leading to high power consumption and cost.
Accordingly, new circuits and methods for spatio-spectral interference mitigation are desirable.